This invention relates to a solid state light modulator structure useful in an apparatus for generating an image from a video input signal, and more particularly relates to such a structure including a deformable metallized elastomer layer, and also relates to a method for metallizing the layer.
U.S. Pat. No. 4,626,920 describes a video display system of the type employing solid state light modulator structures including a deformable, metallized elastomer layer. In this light modulator structure, the deformable layer, for example, a metallized silica-containing gel layer, is disposed over an array of electrodes on the surface of a solid state charge storage device, such as a charge coupled semiconductor device. The metal layer on the surface of the gel serves both as an electrode and as a light reflecting layer.
In operation, electric fields associated with the charge pattern of a stored video frame cause electrostatic attractions between the electrode array and the surface electrode, resulting in deformation of the gel layer in a pattern corresponding to the charge pattern. This pattern is analagous to a phase diffraction grating. The information contained in this pattern is then "read" by reflecting light from the deformed electrode into an optical subsystem such as a Schlieren type of optical system, which then translates the information into a viewable image on a screen.
A critical step in the formation of these light modulator structures is the formation of the light reflective electrode layer on the gel surface. In order for the device to operate successfully, such layer must be electrically conductive, flexible and adherent to the gel layer, and is preferably highly specularly reflective. Unfortunately, since gels are semisolids, having structures which may be characterized as having a liquid phase distributed in an open polymer network, they provide poor surfaces for adhesion.
In the referenced U.S. patent, an electrode layer with the desired characteristics is provided by first providing a thin pellicle layer of nitrocellulose on the gel surface, to provide a surface for adhesion, and to isolate the electrode layer from gel components which could attack and degrade it. Next, a thin intermediate layer of gold is evaporated onto the pellicle layer, followed by evaporation of a thin silver layer onto the gold layer. The gold layer enables the deposition of the silver layer with sufficient uniformity to result in a highly reflective layer.
While it would be desirable from the standpoint of manufacturing efficiency to eliminate the intermediate pellicle and gold layers, it has been found that the deposition of silver directly onto the gel surface by evaporation results in an extremely low specular reflectance, that is, less than one percent. G. C. Martin et al., J. Appl. Phys. 53 (1), 797 (1985).
Accordingly, it is a principal object of the invention to provide a solid state light modulator structure of the type described herein having an adherent, highly reflective metal layer on the surface of the gel layer.
It is another object of the invention to provide a method for forming an adherent, highly reflective metal layer directly onto a silica-containing gel surface without the need for forming intermediate or transitional layers.